Evolution of Resistance to Bt Corn by Western Corn Rootworm: A Tough Management Challenge

Seminar will be given by Dr. Ram Shrestha, Iowa State University, Department of Entomology.

Event will be held in E164 Lagomarcino Hall.

Abstract. Bt technology has been widely used to manage western corn rootworm. Western corn rootworm is known for its ability to adapt to various management practices including Bt corn hybrids. Continuous planting of corn hybrids that produce the same Bt toxin causes multiple generations of intense selection for Bt resistance. Field populations of western corn rootworm in Iowa have developed resistance to multiple Bt toxins. The field-evolved resistance to multiple Bt traits by western corn rootworm has threatened the effectiveness of Bt technology. Thus, it is crucial to develop a better insect resistance management (IRM) strategy that will delay the rate of Bt-resistance evolution and maintain the effectiveness of Bt corn. My goal is to generate knowledge required to develop better IRM strategies to manage Bt-resistant western corn rootworm populations. My research is focused on quantifying Bt resistance in field populations, determining the inheritance and fitness cost of Bt resistance, and measuring the response of Bt-resistant western corn rootworm populations to various management options. With both field and laboratory experiments, I have studied western corn rootworm populations in Iowa that have developed cross-resistance between Cry3Bb1 and mCry3A corn. Single-gene or pyramided Bt corn hybrids that express Cry34/35Ab1 toxin were found to be effective in managing Cry3Bb1-resistant populations. Managing western corn rootworm that are resistant to multiple Bt traits is a big challenge because there is no silver bullet solution for this problem. Adoption of an IPM strategy that includes crop rotation, trait rotation, trait pyramiding, and judicial use of soil insecticide only in non-Bt corn has been recommended

The ENT seminar series is coordinated by Greg Courtney and Rick Hellmich. Please contact either of us with questions related to speakers' visits.